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INVITED SPEAKER SEMINAR - Exploration and Exploitation of Quantum Nonlocality
Date: Friday, March 14, 2025 from 9:00 a.m.
Location: Online event
Abstract
Quantum nonlocality is the most distinguishing feature of quantum mechanics. As the renowned Bell theorem states, there exist quantum correlations between non-communicating nonlocal parties that cannot be explained by any classical means. Exploring such a ‘spooky action at a distance’ provides insights into the nature of quantum theory, motivating the reflection of basic physical notions like randomness. Moreover, exploitation of nonlocality allows quantum physics to realize applications that are infeasible in the classical world, providing approaches to demonstrating quantum advantages in information processing.
In this talk, I will present three results centred on quantum nonlocality. The first finding explores how quantum nonlocality redefines our understanding of causal relationships. To address physical laws that extend beyond classical Bayesian networks and even quantum theory, I will introduce a new causal model inspired by Bell’s theorem. This model encompasses all the possible distributions under general physical theories that comply with Einstein’s principles of relativity. The other two results focus on the implications of quantum nonlocality in computation and cryptography. Towards the final establishment of the ‘magic’ of universal quantum computation, I will discuss how certain computational problems can be reduced into the task of generating nonlocal statistics, thereby establishing quantum computational advantages without relying on intractable assumptions. The last result demonstrates how quantum nonlocality facilitates device-independent cryptographic protocols, which depend solely on the correctness of quantum physics and provide the highest level of security. I will illustrate how to analyse these protocols and exhibit their practical applications.
Biography
Dr. Xingjian Zhang is a postdoctoral research fellow in the Department of Computer Science at the University of Hong Kong, working with Professors Giulio Chiribella and Qi Zhao. He earned his PhD from the Institute for Interdisciplinary Information Sciences at Tsinghua University, where he was supervised by Professor Xiongfeng Ma. Xingjian Zhang is interested in understanding the quantum foundation, establishing high-performance quantum networks, and manifesting certifiable quantum advantages in computation. Thus far, he has published peer-reviewed papers in journals including Nature Communications, Physical Review Letters, PNAS, etc. He has also presented contributed talks at top conferences in quantum information including TQC and AQIS. Based on his research in device-independent quantum information processing, Xingjian Zhang participated in the standardization of quantum information technologies in the International Telecommunication Union (QIT4N-I-018) and in China (GB/T 45240-2025). In addition, Xingjian Zhang has been continuously serving as a peer-review referee for top journals and conferences, including Nature Communications, Physical Review Letters, Science Advances, SODA, etc.